Organizing aplication in layers

Hi!

I’m developing a part of an application, named A. The application I want to plug my DLL into, called application B is in vb 6, and my code is in vb.net. (Application B will in time be converted to vb.net) My main question i, how is the best way for me to organize my code (application A)?

I want to split application A into layers (Service, Business, Data access), so it will be easy to integrate application A into B when B is converted to vb.net. I also want to learn about all the topics like layered architecture, patterns, inversion of dependency, entity framework and so on. Although my application (A) is small I want to organize my cod in the best way.

The application I’m working with (A) is using web services for authenticating users and for sending schema to an organization. The user of application B is selecting a menu point in application B and then some functions in my application A is called.

In application A I have an auto generated schema class from an xsd schema. I fill this schema object with data and serialize the object to a memory string (is it a good solution to use memory string, I don’t have to save the data yet), wrap the xml inside a CDATA block and retur the CDATA block as a string and assign the CDATA block to a string property of a web service.

I am also using Entity framework for database communication (to learn how this is done for the future work with application B). I have to entities in my .edmx, User and Payer. I also want to use the repository pattern (is this a good choice?) to make a façade between the DAL and the BLL.

My application has functions for GeneratingSchema (filling the schema object with data), GetSchemaContent, GetSchemaInformation, GenerateCDATABlock, WriteToTextFile, MemoryStreamToString, EncryptData and some functions that uses web services, like SendShema, AuthenticateUser,GetAvalibelServises and so on.

I’m not sure where I should put it all? I think I have to have some Interfaces like IRepository, ISchema (contract for the auto generated schema class, how can I do this?) ICryptoManager, IFileManager and so on, and classes that implements the interfaces.

My DAL will be the Entity framework. And I want a repository façade in my BLL (IRepository, UserRepository, PayerRepository) and classes for management (like the classes I have mention above) holding functions like WriteToFile, EncryptData …..

Is this a good solution (do I need a service layer, all my GUI is in application B) and how can I organize my layers, interfaces, classes an functions in Visual Studio?

Thanks in advance.